Acoustical apparatus



Nov. 19, 1929. H. L. KENT 1,736,042

ACOUSTICAL APPARATUS Filed Oct. 19, 1925 Patented Nov. 19, 1929 PATENT OFFICE HORACE L. KENT, OF NEW YORK, N. Y.

AGOUSTICAL APPARATUS Application filed October 19, 1925. Serial No. 63,271.

My invention relates particularly to devices such as are used for reproducing instrumental music and vocal sounds.

One object is to provide apparatus which will accurately reproduce sounds of widely differing wave lengths.

Another object is to maintain natural tone qualities and yet give large volume.

Many experiments have convinced me that these objects maybe attained by apparatus such as shown in the accompanying drawings. Conical and pyramidal diaphragms have been used extensively with considerable satisfaction. I have found, however, that greater sensitiveness combined with a wider range of more accurate reproduction and greater volume can be produced by a composite diaphragm consisting of a central pyramidal portion with one or more still larger outwardly flaring frustumed pyramidal portions, all supported at the outer edge. This is preferably mounted within a resonant I casing or housing and vibrated by some suitable means Fig. 1 is a sectional view of the preferred form of apparatus embodying my invention.

Fig. 2 is a fragmentary front view of the same. Figs. 3, and 4 are detail edge and partial sectional views of modified forms of diaphragms.

The diaphragm is preferably formed of some suitable material, such as stiff paper, and in its preferred form consists of a plurality of sections, such as 5, 6, and 7. The central section is pyramidal in form and preferably conical. I have used the term pyramidal in its broad sense of covering a tapered wall regardless of the number of sides in the figure forming its base. When the figure is a circle, of course, the number of sides is infinite. The section 6 is a frustum of a similar pyramidal form with its inclination opposite to the inclination of the central section 5. The section 7 is also a similar frustum of larger diameter withits base preferably in the plane of the base of the cone 5. Preferably the outer edge or perimeter 8 of the diaphragm is reinforced in some suitable manner either by a separate ring or by having its edge of 50 double thickness. The entire diaphragm may be made in one piece or it may be formed of sections suitably secured together at their meeting edges.

I also preferably employ a housing or box of a resonant nature having a base 9 preferably of laminated wood which serves as a sounding board. To this base I secure in any suitable manner a vibrating element 10, in this case in the form of an electro-magnet having an armature 11. This armature is connected to the center of the diaphragm through and may be secure to the medium of a rod 12 which passes through the diaphragm and a wooden post or spindle 13 which is interposed between the diaphragm and the armature. Two washers and a thumb nut 14 may be employed as shown tov clamp the. parts together. The entire diaphragm is preferablydesigned and mounted so as to vibrate as a Whole. For this purpose its edges may be left entirely free. Its edges may however be held in position more or less loosely by a number of cords or wires 15 which may besecured to the side walls 16 of the resonator or housing for instance by means of screw-eyes, such as 17, which can be adjusted if desired. The front of the box may be partially closed by a grill 18 so as to protect the diaphragm if desired.

In the form of diaphragm shown in Fig. 3, the central part 20 instead of being an ordinary cone, is formed as a curved surface, such as the surface of a sphere or a parabola. The outer section 21 may be similarly curved or arched. It will be seen, however, that the inclination of the outer section 21'is reversed to that of the central section 20.

In the form shown in Fig. 4 the central section 22 is in the form of a pyramid having four sides, and the outer section 23 is the frustum of a similar pyramid reversely inclined.

It should be understood that I intend the broader claims to cover a construction having a diaphragm with two or more oppositely inclined sections. In each case, however, the diaphragm is so mounted that it is substantially free at the outer edge and may vibrate as a whole. In this way it is possible to reproduce a very wide range of wave lengths with accuracy and without distortion, and with a maximum volume. It is also very sensitive to microphonic Sounds. The diaphragm isin effect provided with a series of 5 concentric corrugations which stifien it so that it may be made very light in weight and yet strong enough to ensure accurate vibration without causing distortion either of low or high tones. I claim: i

1. A sound reproducer comprising a resonant base, a vibrating device mounted centrally on said resonant base, a conical diaphragm inclined over' and secured to said vibrating device,,a frustumed conical wall connected at its smaller end to said conical diaphragm, and means for positioning the larger end of said wall.

2. A sound reproducer comprising a resonant housing, a vibrator mounted in the rear thereof, a pyramidal diaphragm extending backward around and secured to said vibrator, a wooden post interposed between said diaphragm and said vibrator, and an outwardly flaring diaphragm connected to said pyramidal diaphragm.

3. A sound reproducer comprising a housing having a resonant base, a vibrator rigidly mounted onsaid resonant base, a py- 3 ramidal diaphragm extending backwards around said vibrator connecting meanssecuring. said diaphragm to said vibrator, a

post interposed between said diaphragm and said vibrator and an outwardly flaring diaphragm connected to said pyramidal diaphragm. p

4. A sound reproducer comprising a housing, said housing having aresonant base, a

pyramidal dia hragm extending backward '40 around said vi rator, a rodisecured to said vibrator and said pyramidal diaphragm and an putwardly flaring diaphragm directly connected to said pyramidal diaphragm and indirectly connected to said housingiin'a flexible manner. 7 5. A sound reproducer comprising a reso nant housing, a vibrator mounted on the base of said resonant housing, a paper diaphragm centrally secured to and extending around said vibrator and an outwardly flaring diaphragm directly connected to said paper diaphragm and indirectly connected to said housing.

6. A reproducing box having a resonant base and a latticed cover, a vibrator connected to said resonant base, a pyramidal diaphragm secured to and extending backward towards said vibrator and a flaring diaphragm directly connected to said pyramidal diaphragm and connected to said housing substantially as shown within said reproducing box.

- HORACE L. KENT. 

